The gap between the frame of the widow and the rough opening of the building in which the window is received can be quite large, e.g., as large as 3 inches (˜7.5 cm) or more. Although this gap is normally covered by molding, flashing or other material, additional steps are usually taken to seal this gap against penetration by air and moisture. In some instances, the window installer fills this gap with caulk or polymer foam supplied from a pressured container. In other instances, the installer covers this gap with a sheet of butyl rubber or like elastomer, typically using a pressure sensitive adhesive to adhere the sheet to the window frame and the surrounding building framing members.
Modern industrial windows provide excellent thermal and moisture resistance. Unfortunately, the same cannot be said for the means currently being used to seal the gap between such windows and the rough opening in which they are received. Caulk becomes largely ineffective when the gap is larger than about 1 inch (˜2.54 cm). Insulating foam cannot accommodate joint movement and can degrade over time. Elastomeric sheets, meanwhile, can be difficult to lay down evenly and uniformly, especially at the window's corners. For example, elastomeric sheets are typically folded over on themselves, substantially puckered or multiply overlapped to get them to fit it into proper position at the window's corner. This often prevents a good seal from being formed due to the excessive or extra material involved.